2 cards are drawn from a pack of 52 cards. Find the probalility that one of these is an ace and the other is a queen of opposite shade.

The chances of a queen are 4/52, or 1/13

The chances of an ace of the opposite shade are 2/51

So 2/(13*51), or 2/663

But you could also draw the ace first (1/13) and then the queen of the opposite shade (2/15) for the same 2/663 chance.

either order will do, so there’s a 2/663+2/663=4/663 overall chance of drawing those two cards, order unimportant.